Multi-speed power tool transmission

ABSTRACT

A multi-speed transmission assembly for a rotary power tool. The transmission assembly includes a plurality of transmission stages, with at least two of the transmission stages employing a movable reduction element that permits the transmission stage to be operated in an active mode and an inactive mode. The movable reduction elements are coupled to a switching mechanism that switches the reduction elements in a predetermined manner to provide at least three-gear reduction or speed ratios.

PRIORITY & CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/263,379, filed Jan. 23, 2001. Other features of the present inventionare discussed and claimed in commonly assigned copending U.S.application Ser. No. 09/964,028 entitled First Stage Clutch; U.S.application Ser. No. 09/965,108 entitled 360 Degree Clutch Collar; andU.S. application Ser. No. 09/963,905 entitled Housing with FunctionalOvermold Member.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to power tools such as rotatabledrills, power screwdrivers, and rotatable cutting devices. Moreparticularly, the present invention relates to a transmission for amulti-speed transmission for a rotary power tool.

2. Discussion

Modernly, manufacturers of power tools have introduced rotary powertools that have variable speed motors in an attempt to permit the usersof these tools with sufficient control over the output speed of the toolso as to permit them to perform diverse operations without resort toadditional, specialized tools. Many of the tools that are commerciallyavailable include a three-stage, two-speed transmission that permitseven greater control over speeds of these tools.

Typically, the known transmission arrangements have lacked atransmission arrangement that could produce a wide range of outputspeeds and torques that would permit the tool to perform diverseoperations such as drilling holes with a large diameter hole saw,installing drywall screws or large diameter lag screws, and performinghigh-speed drilling operations. The single or dual speed transmissionsthat were generally employed in these tools typically did not havesufficient speed reducing capacity to permit these transmissions to bediversely employed as configuring these tools for high torque operationstended to impair their high speed performance. Furthermore, therechargeable batteries that were employed in many of the early cordlessrotary power tools were not well suited for use in low-speed, hightorque operations due to the amount of energy that is consumed and therate with which the energy is consumed by the power tool during suchoperations. Consequently, consumers were often forced to purchase twodifferent rotary power tools, a medium-duty tool for “standard”applications such as drilling and fastening, and a heavy-duty toolhaving a low-speed, high torque output for more demanding tasks.

With the advent of the modern high capacity, high voltage battery, it isnow possible to meet the energy demands of a power tool that is used inlow-speed, high torque operations. There remains, however, a need in theart for a power tool transmission having a relatively large range in itsspeed reducing capacity.

SUMMARY OF THE INVENTION

In one preferred form, the present invention provides a drive train fora power tool. The drive train includes a housing, a transmission and aspeed selector mechanism. The transmission has first, second and thirdreduction gear sets, with two of the reduction gear sets beingconfigured to operate in an active mode for performing a speed reductionand torque multiplication operation and an inactive mode. The speedselector mechanism has a switch portion that is coupled to the housingfor movement between first, second and third positions and an actuatorportion that is coupled to the transmission. The actuator portion isconfigured to move two of the reduction gear sets between the active andinactive modes in response to movement of the switch portion between thefirst, second and third positions.

In another preferred form, the present invention provides a transmissionassembly for transmitting torque to an output shaft in a power tool. Thetransmission assembly includes a housing, a first transmission portionand a second transmission portion. The housing includes a wall memberthat defines a transmission bore. The first transmission portion has afirst input member, a first output member and a first reduction element.The first input member is configured to receive a first intermediateoutput torque and the first output member configured to output a secondintermediate output torque. The first reduction element operable in afirst condition wherein the first transmission portion multiplies thefirst intermediate output torque by a predetermined first amount. Thefirst reduction element further operable in a second condition whereinthe first transmission portion multiplies the first intermediate outputtorque by a predetermined second amount. The second transmission portionincludes a second input member, a second output member and a secondreduction element. The second input member is configured to receive thesecond intermediate output torque and the second output memberconfigured to output an output torque to the output shaft. The secondreduction element operable in a first condition wherein the secondtransmission portion multiplies the second intermediate output torque bya predetermined third amount. The second reduction element furtheroperable in a second condition wherein the second transmission portionmultiplies the second intermediate output torque by a predeterminedfourth amount.

In yet another preferred form, the present invention provides a powertool having a motor and a transmission. The motor has an output shaftand produces an input torque. The transmission assembly has a housinghaving a wall member that defines a transmission bore and a transmissionhaving first, second and third planetary gear sets. The first planetarygear set has a first ring gear, a first sun gear and a first planet gearassembly. The first planet gear assembly has a first planet carrier anda plurality of first planet gears. The first planet carrier rotatablycoupled to the first sun gear. The first planet carrier has a pluralityof pinions for rotatably supporting the plurality of first planet gears.The first sun gear is configured to receive the input torque. The firstplanet carrier includes a second sun gear and being configured totransmit the first intermediate output torque to the second planetarygear set. The plurality of first planet gears meshingly engaged with thesecond sun gear and the first ring gear. The first ring gear axiallypositionable in a first condition wherein the first ring gear is fixedrelative to the housing.

The second planetary gear set includes a second ring gear and a secondplanet gear assembly. The second planet gear assembly has a secondplanet carrier and a plurality of second planet gears. The second planetcarrier has an output sun gear and a plurality of pinions for rotatablysupporting the plurality of second planet gears. The second sun gear ismeshingly engaged with the plurality of second plane gears and transmitsthe first intermediate output torque thereto. The output sun gearconfigured to output a second intermediate output torque. The pluralityof second planet gears are also meshingly engaged with the second ringgear. The second ring gear is axially positionable in a first conditionwherein the second ring gear is fixed relative to the housing to preventrelative rotation therebetween. The second ring gear is also axiallypositionable in a second condition wherein the second ring gear isrotatable within the transmission bore.

The third planetary gear set includes a third ring gear and a thirdplanet gear assembly. The third planet gear assembly has a third planetcarrier and a plurality of third planet gears. The third planet carrierhas an output member and a plurality of pinions that rotatably supportthe plurality of third planet gears. The plurality of third planet gearsare meshingly engaged with the third ring gear and the output sun gearand are configured to receive the second intermediate output torque. Theoutput member is configured to output an output torque. The third ringgear is axially positionable in a first condition wherein the third ringgear is fixed relative to the housing to prevent relative rotationtherebetween. The third ring gear is also axially positionable in asecond condition wherein the third ring gear is rotatable within thetransmission bore.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages and features of the present invention will becomeapparent from the subsequent description and the appended claims, takenin conjunction with the accompanying drawings, wherein:

FIG. 1 is a side view of a power tool constructed in accordance with theteaching of the present invention;

FIG. 2 is an exploded perspective view of a portion of the power tool ofFIG. 1;

FIG. 3 is a perspective view of a portion of the housing of the powertool of FIG. 1 illustrating the rear of the end cap assembly;

FIG. 4 is a front view of the end cap assembly;

FIG. 5 is a section view taken along the line 5—5 of FIG. 4;

FIG. 6 is a rear view of a portion of the power tool of FIG. 1 with theend cap assembly removed;

FIG. 7 is a side view of a portion of the power tool of FIG. 1 with theend cap assembly removed;

FIG. 8 is a view similar to that of FIG. 4, but illustrating the end capshell prior to the overmolding operation;

FIG. 9 is a view similar to that of FIG. 5, but illustrating the end capshell prior to the overmolding operation;

FIG. 10 is a view similar to that of FIG. 4, but illustrating analternate construction of the overmold member;

FIG. 11 is a partial sectional view of a portion of a power tool thatemploys an end cap assembly having an overmold member constructed in themanner illustrated in FIG. 10;

FIG. 12 is an exploded perspective view of a portion of the power toolof FIG. 1, illustrating the transmission assembly in greater detail;

FIG. 13 is an exploded perspective view of a portion of the power toolof FIG. 1, illustrating the reduction gearset assembly, the transmissionsleeve, a portion of the housing and a portion of the clutch mechanismin greater detail;

FIG. 13a is a sectional view taken along a longitudinal axis of thesecond ring gear;

FIG. 13b is a sectional view taken along a longitudinal axis of thethird ring gear;

FIG. 14 is a side view of the transmission sleeve;

FIG. 15 is a rear view of the transmission sleeve;

FIG. 16 is a sectional view taken along the line 16—16 of FIG. 15;

FIG. 17 is a sectional view taken along the line 17—17 of FIG. 15;

FIG. 18 is an exploded view of the reduction gearset assembly;

FIG. 19 is a sectional view taken along a longitudinal axis of the powertool of FIG. 1 illustrating a portion of the reduction gearset assemblyin greater detail;

FIG. 20 is a front view of a portion of the first reduction carrier;

FIG. 21 is a sectional view taken along a longitudinal axis of the powertool of FIG. 1 illustrating a portion of the reduction gearset assemblyin greater detail;

FIG. 22 is a rear view of a portion of the third reduction carrier;

FIG. 23 is an sectional view taken along the longitudinal axis of thepower tool of FIG. 1 and illustrating the transmission assembly aspositioned in the first speed ratio;

FIG. 24 is a sectional view similar to that of FIG. 23 but illustratingthe transmission assembly as positioned in the second speed ratio;

FIG. 25 is a sectional view similar to that of FIG. 23 but illustratingthe transmission assembly as positioned in the third speed ratio;

FIG. 26 is a top view of a portion of the power tool of FIG. 1illustrating the speed selector mechanism in greater detail;

FIG. 27a is a side view of the rotary selector cam;

FIG. 27b is a top view of the rotary selector cam;

FIG. 27c is a sectional view taken through along the central axis of thespeed selector mechanism;

FIG. 28 is a rear view of the output spindle assembly;

FIG. 29 is an exploded perspective view of the clutch mechanism;

FIG. 29a is a perspective view of a portion of the clutch mechanismillustrating another configuration of the clutch member;

FIG. 29b is an exploded perspective view illustrating a multi-piececonstruction for the first ring gear and clutch member;

FIG. 30 is a schematic illustration of the adjustment structure in an“unwrapped” state;

FIG. 31 is a schematic illustration similar to that of FIG. 30 butshowing an alternate construction of the adjustment profile; and

FIG. 32 is a schematic illustration similar to that of FIG. 30 butshowing a portion of another alternate construction of the adjustmentprofile;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Overview

With reference to FIGS. 1 and 2 of the drawings, a power toolconstructed in accordance with the teachings of the present invention isgenerally indicated by reference numeral 10. As those skilled in the artwill appreciate, the preferred embodiment of the present invention maybe either a cord or cordless (battery operated) device, such as aportable screwdriver or drill. In the particular embodiment illustrated,power tool 10 is a cordless drill having a housing 12, a motor assembly14, a multi-speed transmission assembly 16, a clutch mechanism 18, anoutput spindle assembly 20, a chuck 22, a trigger assembly 24 and abattery pack 26. Those skilled in the art will understand that severalof the components of power tool 10, such as the chuck 22, the triggerassembly 24 and the battery pack 26, are conventional in nature and neednot be described in significant detail in this application. Referencemay be made to a variety of publications for a more completeunderstanding of the operation of the conventional features of powertool 10. One example of such publications is commonly assigned U.S. Pat.No. 5,897,454 issued Apr. 27, 1999, the disclosure of which is herebyincorporated by reference as if fully set forth herein.

Housing 12 includes an end cap assembly 30 and a handle shell assembly32 that includes a pair of mating handle shells 34. Handle shellassembly 32 includes a handle portion 36 and a drive train or bodyportion 38. Trigger assembly 24 and battery pack 26 are mechanicallycoupled to handle portion 36 and electrically coupled to motor assembly14. Body portion 38 includes a motor cavity 40 and a transmission cavity42. Motor assembly 14 is housed in motor cavity 40 and includes arotatable output shaft 44, which extends into transmission cavity 42. Amotor pinion 46 having a plurality of gear teeth 48 is coupled forrotation with output shaft 44. Trigger assembly 24 and battery pack 26cooperate to selectively provide electric power to motor assembly 14 ina manner that is generally well known in the art so as to control thespeed and direction with which output shaft 44 rotates.

Transmission assembly 16 is housed in transmission cavity 42 andincludes a speed selector mechanism 60. Motor pinion 46 couplestransmission assembly 16 to output shaft 44, transmitting a relativelyhigh speed, low torque drive input to transmission assembly 16.Transmission assembly 16 includes a plurality of reduction elements thatare selectively engaged by speed selector mechanism 60 to provide aplurality of speed ratios. Each of the speed ratios multiplies the speedand torque of the drive input in a predetermined manner, permitting theoutput speed and torque of the transmission assembly 16 to be varied ina desired manner between a relatively low speed, high torque output anda relatively high speed, low torque output. The transmission output isdelivered the output spindle assembly 20, to which the chuck 22 iscoupled for rotation, to permit torque to be transmitted to a tool bit(not shown). The clutch mechanism 18 is coupled to transmission assembly16 and is operable for limiting the magnitude of the torque associatedwith the drive input to a predetermined, selectable torque limit.

Functional Overmold

With specific reference to FIGS. 2 through 9, end cap assembly 30 isshown to include an end cap shell 100 and an overmold member 102. In theexample provided, the end cap shell 100 is injection molded from aplastic material, such as ABS. The end cap shell 100 defines an end capcavity 104 that is sized to receive the portion of the motor assembly 14that extends rearwardly of the handle shell assembly 32. A plurality offirst and second radial tab apertures 108 and 110 and the abutting face128 are formed into the forward face 114 of the end cap shell 100 and aplurality of screw bosses 116 are formed into the perimeter of the endcap shell 100. Each of the first and second radial tab apertures 108 and110 is sized to receive one of the first radial tabs 120 and secondradial tabs 122, respectively, that are formed into the rearward face124 of the handle shells 34. The first and second radial tab apertures108 and 110 cooperate with the first and second radial tabs 122 toproperly align the end cap shell 100 to the handle shell assembly 32, aswell as to inhibit relative rotation therebetween. An arcuate portion128 of the forward face 114 of the end cap shell 100 is angled to matchthe abutting face 132 of the rearward face 124 of the handle shells 34.The screw bosses 116 permit the end cap shell 100 to be fixedly coupledto the motor cover 136 via a plurality of screws 138. The geometry ofthe motor cover 136 is such that it is constrained to the handle shells34. As such, fastening of the end cap shell 100 to the motor cover 136operates to fixedly retain the end cap shell 100 against as the rearwardface 124 of the handle shell assembly 32, as well as to close off therear handle aperture 139 in the handle shell assembly 32.

A plurality of side apertures 140 are formed into the sides of the endcap shell 100 to permit air to flow through the handle shell assembly 32and cool the motor assembly 14 in a manner that is well known in theart. A plurality of rear apertures 144 are formed into the rear of theend cap shell 100, with each of the rear apertures 144 including arecessed portion 146 that extends only partially into the outer surface148 of the end cap shell 100 and a through-portion 150 that extendscompletely through the end cap shell 100. A pair of retaining tabs 152are formed to extend from the interior surface 154 of the end cap shell100 inwardly into the end cap cavity 104. A channel 156 is formed intothe interior surface 154 of the end cap shell 100 and intersects each ofthe rear apertures 144 and the retaining tabs 152.

The overmold member 102 is formed from a resilient material, such asthermoplastic elastomer (e.g., HYTREL® manufactured by E. I. du Pont deNemours and Company) and is simultaneously formed and coupled to the endcap shell 100 in an injection molding operation. In the particularexample provided, the overmold member 102 includes a plurality of bumpermembers 170, a pair of isolators 172 and a linking member 174. Each ofthe bumper members 170 extends from a point roughly coincident with theinterior surface 154 of the end cap shell 100 to a point rearwardly ofthe outer surface 148 of the end cap shell 100 by about 0.5 mm to about1.5 mm and preferably about 0.75 mm. Construction in this manner permitsthe bumper members 170 to provide a degree of shock absorption whichreduces the likelihood of damaging the end cap shell 100 in the eventthat the tool 10 is dropped. Furthermore, it is sometimes necessary foran operator to apply a relatively high force to the tool 10, as whenemploying a hole saw to drill large diameter holes. In such situations,the operator is inclined to press onto the rear of the tool 10 to applya force that is in-line with the axis of the chuck 22. In suchsituations, the bumper members 170 provide the operator with arelatively soft and comfortable surface which tends to resist slippingas well as attenuate the vibrations that are transmitted to theoperator.

The isolators 172 are formed about the retaining tabs 152 on theinterior surface 154 of the end cap shell 100. In the example provided,each of the isolators 172 includes an annular member 180 that extendsforwardly of the interior surface 154 of the end cap shell 100.Construction in this manner permits the end cap shell 100 to engage theisolators 172 to the outer diameter 14 a and the rear surface 14 b ofthe motor housing 14 c to fixedly retain the motor 14 d within the motorcover 136. This prevents the components of the motor assembly 14 frommoving along the longitudinal axis of the tool 10, as well as dampensvibrations that are created during the operation of the motor assembly14. The linking member 174 is fixedly coupled to each of the bumpermembers 170 and the isolators 172. The linking member 174 provides aflow path through which the resilient material flows during theformation of the bumper members 170 and the isolators 172. The linkingmember 174 also interconnects the bumper members 170 and the isolators172, thereby rendering their removal from the end cap shell 100 moredifficult.

Those skilled in the art will appreciate that this aspect of the presentinvention may be incorporated into various other positions within thehandle assembly 32 for sealing between two or more components, dampeningvibrations or positioning one component relative to another. One suchexample is illustrated in FIGS. 10 and 11 where the isolators 172 aremodified to extend around the perimeter of a portion of the end capcavity 104 and sealingly contact the rear surface 14 b of the motor 14d. The isolators 172 seal the interface between the end cap shell 100and the motor assembly 14, while the bumper members 170 seal the rearapertures 144 in the end cap shell 100. The space 188 defined by theisolators 172 is then filled with grease or another suitable lubricant,which lubricates a motor armature bearing 190.

Transmission Assembly

With reference to FIG. 12, the transmission assembly 16 is shown to be athree-stage, three-speed transmission that includes a transmissionsleeve 200, a reduction gearset assembly 202 and the speed selectormechanism 60. With additional reference to FIGS. 13 through 17, thetransmission sleeve 200 includes a wall member 210 that defines agenerally transmission bore or hollow cavity 212 into which thereduction gearset assembly 202 is disposed. The transmission sleeve 200includes a body 214 and a base 216. The body 214 of the transmissionsleeve 200 is fairly uniform in diameter and generally smaller indiameter than the base 216. The inside diameter of the base 216 is sizedto receive the cylindrical nose portion 220 of the motor cover 136.

A plurality of raised lands 226 are formed into the base 216. The raisedlands 226 define a plurality of first grooves 228 in the outer surface230 of the base 216 and a plurality of second grooves 232 in the innersurface 234 of the base 216. The first grooves 228 are configured toreceive the alignment ribs 238 that are formed into the inner surface242 of the handle shells 34 to align the transmission sleeve 200 to thehandle shells 34 and inhibit relative rotation between the transmissionsleeve 200 and the housing 12. Preferably, the first grooves 228 andalignment ribs 238 are configured in a manner that the transmissionsleeve 200 can only be assembled to the handle shells 34 in oneorientation (i.e., the configuration of the first grooves 228 andalignment ribs 238 prevents the transmission sleeve 200 from beingrotated 180° out of position relative to the handle shells 34). Thesecond grooves 232 will be discussed in greater detail, below.

The body 214 of the transmission sleeve 200 is shown to include acylindrical body portion 246 and a pin housing portion 248. In theparticular embodiment illustrated, the cylindrical body portion 246includes a selector cam guide 250, a plurality of lubricant grooves 252and first and second sets of ring engagement teeth 254 and 256,respectively. The selector cam guide 250 is generally rectangular incross section, extending outwardly from the top of the outer surface 258of the body portion 246. The lubricant grooves 252 are formedconcentrically around the upper half of the perimeter of the bodyportion 246. The lubricant grooves 252 have a depth of about 0.01 inchto about 0.030 inch to hold a lubricant, such as grease, on the upperhalf of the perimeter of the body portion 246. The operation of theselector cam guide 250 and the lubricant grooves 252 will be discussedin detail, below.

A raised bead 264 segregates the interior of the body portion 246 intofirst and second housing portions 260 and 262, respectively. The firstset of ring engagement teeth 254 are formed onto the inner surface 266of the body portion 246 and extend rearwardly from the raised bead 264toward the base 216. The second set of ring engagement teeth 256 arealso formed into the inner surface of the body portion 246 but extendforwardly from the raised bead 264. The teeth 268 of the first andsecond sets of ring engagement teeth 254 and 256 are uniformly spacedaround the inner surface 266 of the body portion 246. The configurationof each tooth 268 in the first and second sets of ring engagement teeth254 and 256 is similar in that each tooth extends from the raised bead264, has a pair of parallel engagement surfaces 270 and terminates at atip portion 272. The tip portion 272 of each tooth 268 is both roundedand tapered to enhance the ability with which it will mesh with aportion of the reduction gearset assembly 202 as will be described indetail, below.

The pin housing portion 248 extends downwardly from the body portion 246over a significant portion of the length of the body portion 246. Anactuator aperture 274 is formed into the pin housing portion 248 andextends rearwardly through the base 216 of the transmission sleeve 200.In the particular embodiment illustrated, the actuator aperture 274 isstepped, having a first portion 276 with a first diameter at the rear ofthe transmission sleeve 200 and a second portion 278 with a smallersecond diameter at the front of the transmission sleeve 200. In theexample shown, the first portion 276 of the actuator aperture 274 breaksthrough the wall of the first housing portion 260 and forms a groove 280into the inner surface 234 of the base 216. The pin housing portion 248will be discussed in further detail, below.

A pair of first clip slots 284 and a pair of second clip slots 286 areformed into the transmission sleeve 200, extending along the sides ofthe transmission sleeve 200 in a manner that is parallel thelongitudinal axis of the transmission sleeve 200. The first pair of clipslots 284 is formed through the sides of the body portion 246 rearwardlyof the raised bead 264 and extends rearwardly toward the base 216. Thedepth of the first pair of clip slots 284 is such that they do notextend through the portion of the wall member 210 that defines the base216. The second pair of clip slots 286 are also formed through the sidesof the body portion 246 beginning forwardly of the raised bead 264 andextending through the front face 288 of the transmission sleeve 200.

With reference to FIGS. 12, 13, 18 and 23, the reduction gearsetassembly 202 includes a first reduction gear set 302, a second reductiongear set 304 and a third reduction gear set 306. The first, second andthird reduction gear sets 302, 304 and 306 are operable in an activemode and an inactive mode. Operation in the active mode causes thereduction gear set to perform a speed reduction and torquemultiplication operation, while operation of the reduction gear set inan inactive mode for causes the reduction gear set to provide an outputhaving a speed and torque that is about equal to the speed and torque ofthe rotary input provided to that reduction gear set. In the particularembodiment illustrated, each of the first, second and third reductiongear sets 302, 304 and 306 are planetary gear sets. Those skilled in theart will understand, however, that various other types of reduction gearsets that are well known in the art may be substituted for one or moreof the reduction gear sets forming the reduction gearset assembly 202.

As shown, the first reduction gear set 302 includes a first reductionelement or ring gear 310, a first set of planet gears 312 and a firstreduction carrier 314. The first ring gear 310 is an annular structure,having a plurality of gear teeth 310 a formed along its interiordiameter. A clutch face 316 is formed into the outer perimeter of thefront face 318 of the first ring gear 310 and will be discussed ingreater detail, below. The first ring gear 310 is disposed within theportion of the hollow cavity 212 defined by the base 216; the front face318 of the first ring gear 310 contacts a step 320 formed into thetransmission sleeve 200, thereby limiting the ability of the first ringgear 310 to move forwardly into the hollow cavity 212.

The first reduction carrier 314 is formed in the shape of a flatcylinder, having plurality of pins 322 that extend from its rearwardface 324. A plurality of gear teeth 314 a are formed into almost theentire outer perimeter of the first reduction carrier 314, with a valley314 b being formed between each pair of adjacent gear teeth 314 a. Dueto the spacing of the gear teeth 314 a, one of the valleys (i.e., valley314 b′) is relatively larger than the remaining valleys 314 b due to theomission of a tooth 314 a in the outer perimeter of the first reductioncarrier 314. In the particular embodiment illustrated, the gear teeth314 a of the first reduction carrier 314 are configured so as not to bemeshingly engagable with the gear teeth 310 a of the first ring gear310.

With specific reference to FIGS. 19 and 20, the profile of the gearteeth 314 a is illustrated in greater detail. As shown, each gear tooth314 a terminates at a gradual radius 326 at the forward face 328 of thefirst reduction carrier 314 but terminates abruptly at the rearward face324 of the first reduction carrier 314. A radius 330 is also formed onthe valleys 314 b between the gear teeth 314 a.

Returning to FIGS. 12, 13, 15, 18 and 23, a first thrust washer 332having a first annular portion 334, a second annular portion 336 and aplurality of retaining tabs 338 is positioned rearwardly of the firstreduction gear set 302. The retaining tabs 338 engage the second grooves232 in the base 216 of the transmission sleeve 200 and as such, relativerotation between the first thrust washer 332 and the transmission sleeve200 is inhibited. The inside diameter of the base 216 is sized toreceive the motor cover 136 and as such, the front face 340 of the motorcover 136 inhibits the axial movement of the first thrust washer 332.The first annular portion 334 contacts the rear face 342 of the firstring gear 310, providing a wear surface and controlling the amount bywhich the first ring gear 310 is able to move in an axial direction. Thesecond annular portion 336 is spaced axially apart from the firstannular portion 334, extending forwardly of the first annular portion334 to provide a wear surface for the first set of planet gears 312 thatalso controls the amount by which they can move in an axial direction.

The first set of planet gears 312 includes a plurality of planet gears344, each of which being generally cylindrical in shape, having aplurality of gear teeth 344 a formed into its outer perimeter and a pinaperture 346 formed its their center. Each planet gear 344 is rotatablysupported on an associated one of the pins 322 and the first reductioncarrier 314 and is positioned such that its teeth 344 a meshingly engagethe teeth 314 a of the first ring gear 310. A raised portion 348 isformed into the front and rear face 350 and 352 of each planet gear 344that inhibits the teeth 344 a from rubbing on the first reductioncarrier 314 and the first thrust washer 332 and creating dust or chipsthat would impair the performance of the transmission assembly 16 andreduce its operating life. As the teeth 46 a of the motor pinion 46 onthe output shaft 44 are also meshingly engaged with the teeth 344 a ofthe planet gears 344, the motor pinion 46 serves as a sun gear for thefirst reduction gear set 302.

The second reduction gear set 304 is disposed within the portion of thehollow cavity 212 defined by the first housing portion 260 and includesa second sun gear 358, a second reduction element or ring gear 360, asecond set of planet gears 362 and a second reduction carrier 364. Thesecond sun gear 358 is fixed for rotation with the first reductioncarrier 314. The second sun gear 358 includes a plurality of gear teeth358 a that extend forwardly of the forward face 328 of the firstreduction carrier 314.

The second ring gear 360 is an annular structure, having a plurality ofgear teeth 360 a formed along its interior diameter. The gear teeth 360a may be heavily chamfered at the rear face 366 of the second ring gear360 but terminate abruptly at the front face 368. More preferably, aheavy radius 369 is formed onto the rear face 366 and the sides of eachof the gear teeth 360 a, with the heavy radius 369 being employed ratherthan the heavy chamfer as the heavy radius 369 on the gear teeth 360 aprovides for better engagement between the second ring gear 360 and thefirst reduction carrier 314.

A plurality of sleeve engagement teeth 370 are formed into the outerperimeter of the second ring gear 360; the sleeve engagement teeth 370extend forwardly toward the front face 368 of the second ring gear 360and terminate at a tip portion 372 that is rounded and tapers forwardlyand inwardly. An annular clip groove 374 is also formed into the outerperimeter of the second ring gear 360. In the example illustrated, theclip groove 374 is a rectangular slot having a pair of sidewalls 376.The clip groove 374 will be discussed in greater detail, below.

The second reduction carrier 364 is formed in the shape of a flatcylinder, having plurality of pins 378 that extend from its rearwardface 380. The second set of planet gears 362 is shown to include aplurality of planet gears 382. Each planet gear 382 is generallycylindrical in shape, having a plurality of gear teeth 382 a formed intoits outer perimeter and a pin aperture 384 formed its center. Eachplanet gear 382 is rotatably supported on an associated one of the pins378 and the second reduction carrier 364 is positioned such that thegear teeth 382 a of the planet gears 382 meshingly engage the gear teeth360 a of the second ring gear 360. The gear teeth 358 a of the secondsun gear 358 are also meshingly engaged with the gear teeth 382 a of theplanet gears 382.

The third reduction gear set 306 is disposed within the portion of thehollow cavity 212 defined by the second housing portion 262 and includesa third sun gear 398, a third reduction element or ring gear 400, athird set of planet gears 402 and a third reduction carrier 404. Thethird sun gear 398 is fixed for rotation with the second reductioncarrier 364. The third sun gear 398 includes a plurality of gear teeth398 a that extend forwardly of the front face 406 of the secondreduction carrier 364.

The third ring gear 400 is an annular structure, having a plurality ofgear teeth 400 a formed along its interior diameter. The gear teeth 400a may be heavily chamfered at the front face 412 of the third ring gear400, but terminate abruptly at the rear face 414. More preferably, aheavy radius 407 is formed onto the front face 412 and the sides of eachof the gear teeth 400 a, with the heavy radius 407 being employed ratherthan the heavy chamfer as the heavy radius 407 on the gear teeth 400 aprovides for better engagement between the third ring gear 400 and thethird reduction carrier 404. A plurality of sleeve engagement teeth 418are formed into the outer perimeter of the third ring gear 400; thesleeve engagement teeth 418 extend rearward toward the rear face 414 ofthe third ring gear 400 and terminate at a tip portion 420 that isrounded and tapers rearwardly and inwardly. An annular clip groove 422is also formed into the outer perimeter of the third ring gear 400. Inthe example illustrated, the clip groove 422 is a rectangular slothaving a pair of sidewalls 424. The clip groove 422 will be discussed ingreater detail, below.

The third reduction carrier 404 is formed in the shape of a flatcylinder, having plurality of pins 428 that extend from its rearwardface 430. A plurality of gear teeth 404 a are formed into almost theentire outer perimeter of the third reduction carrier 404, with a valley404 b being formed between each pair of adjacent teeth 404 a. Due to thespacing of the teeth 404 a, one of the valleys 404 b (i.e., valley 404b′) is relatively larger than the remaining valleys 404 b due to theomission of a tooth 404 a in the outer perimeter of the third reductioncarrier 404. In the particular embodiment illustrated, the gear teeth404 a of the third reduction carrier 404 are configured so as not to bemeshingly engagable with the gear teeth 382 a of the second planet gears382.

With brief additional reference to FIGS. 21 and 22, the profile of thegear teeth 404 a is illustrated in greater detail. As shown, the rearface 430 of the third reduction carrier 404 is chamfered and a heavyradius 434 is formed into each of sides of the teeth 404 a and valleys404 b. Each gear tooth 404 a terminates abruptly at the forward face 436of the third reduction carrier 404.

Returning back to FIGS. 12, 13, 15, 18 and 23, the third set of planetgears 402 is shown to include a plurality of planet gears 438. Eachplanet gear 438 is generally cylindrical in shape, having a plurality ofgear teeth 438 a formed into its outer perimeter and a pin aperture 440formed through its center. Each planet gear 438 is rotatably supportedon an associated one of the pins 428 and the third reduction carrier 404is positioned such that the gear teeth 438 a of the planet gears 438meshingly engage the gear teeth 400 a of the third ring gear 400. Araised portion 442 is formed into each of the front and rear faces ofthe planet gears 438 which inhibits the gear teeth 438 a from rubbing onthe third reduction carrier 404 and creating dust or chips that wouldimpair the performance of the transmission assembly 12 and reduce itsoperating life. A second thrust washer 450 is disposed around the thirdsun gear 398 and the teeth 398 a of the third sun gear 398 are meshinglyengaged with the gear teeth 438 a of the planet gears 438. The secondthrust washer 450 includes a plurality of retaining tabs 452 that areconfigured to engage corresponding tab grooves 454 (FIG. 13) that areformed in the inner surface 266 of body portion 246 of the transmissionsleeve 200. The retaining tabs 452 and the tab grooves 454 cooperate toinhibit relative rotation between the second thrust washer 450 and thetransmission sleeve 200.

The output spindle assembly 20 includes a transmitting means 458 forcoupling a spindle 460 for rotation with the third reduction carrier 404so as to transmit drive torque from the reduction gearset assembly 202to the chuck 22. Such transmitting means 458 are well known in the artand easily adapted to the transmission assembly of the presentinvention. Accordingly, a detailed discussion of the transmitting means458 need not be included herein.

With reference to FIGS. 13, 13 a, 13 b, 16, 17, 18 and 23 through 28,the speed selector mechanism 60 is movable between a first position 500,a second position 502 and a third position 504 and includes a switchportion 510 for receiving a speed change input and an actuator portion512 for manipulating the reduction gearset assembly 202 in accordancewith the speed change input. The actuator portion 512 is operativelycoupled to the reduction gearset assembly 202 and moves the second andthird reduction gear sets 304 and 306 between the active and inactivemodes in response to movement of the switch portion 510 between thefirst, second and third positions 500, 502 and 504. In the particularembodiment illustrated, the actuator portion 512 includes a rotaryselector cam 520, a plurality of wire clips 522 and a spring member 523.Each of the wire clips 522 is formed from a round wire which is bent inthe shape of a semi-circle 524 with a pair of tabs 526 extendingoutwardly from the semi-circle 524 and positioned on about thecenterline of the semi-circle 524. The semi-circle 524 is sized to fitwithin the clip grooves 374 and 422 in the second and third ring gears360 and 400, respectively. In this regard, the semi-circle 524 neitherextends radially outwardly of an associated one of the ring gears (360,400), nor binds against the sidewalls (376, 424) of the clip grooves(374, 422). In the example provided, the sidewalls (376, 424) of theclip grooves (374, 422) are spaced apart about 0.05 inch and thediameter of the wire forming the wire clips 522 is about 0.04 inch.

The tabs 526 of the wire clips 522 extend outwardly of the hollow cavity212 into an associated one of the clip slots (284, 286) that is formedinto the transmission sleeve 200. The tabs 526 are long enough so thatthey extend outwardly of the outer surface 258 of the body 214 of thetransmission sleeve 200, but not so far as to extend radially outwardlyof the portion of the first clip slots 284 in the base 216 of thetransmission sleeve 200. Configuration of the wire clips 522 in thismanner facilitates the assembly of the transmission assembly 16,permitting the wire clips 522 to be installed to the second and thirdring gears 360 and 400, after which these assemblies are inserted intothe hollow cavity 212 along the longitudinal axis of the transmissionsleeve 200.

With specific reference to FIGS. 13 and 27a through 27 c, the rotaryselector cam 520 is illustrated to include an arcuate selector body 530,a switch tab 532 and a plurality of spacing members 534. A pair of firstcam slots 540 a and 540 b, a pair of second cam slots 544 a and 544 b, aspring aperture 546 and a guide aperture 548 are formed through theselector body 530. The selector body 530 is sized to engage the outsidediameter of the body portion 246 of the transmission sleeve 200 in aslip-fit manner. The guide aperture 548 is generally rectangular inshape and sized to engage the front and rear surfaces of the selectorcam guide 250. The guide aperture 548 is considerably wider than thewidth of the selector cam guide 250, being sized in this manner topermit the rotary selector cam 520 to be rotated on the transmissionsleeve 200 between a first rotational position, a second rotationalposition and a third rotational position. The selector cam guide 250 andcooperates with the guide aperture 548 to limit the amount by which therotary selector cam 520 can be rotated on the transmission sleeve 200,with a first lateral side of the selector cam guide 250 contacting afirst lateral side of the guide aperture 548 when the rotary selectorcam 520 is positioned in the first rotational position, and a secondlateral side of the selector cam guide 250 contacting a second lateralside of the guide aperture 548 when the rotary selector cam 520 ispositioned in the third rotational position.

Each of the first cam slots 540 a and 540 b is sized to receive one ofthe tabs 526 of the wire clip 522 that is engaged to the second ringgear 360. In the particular embodiment illustrated, first cam slot 540 aincludes a first segment 550, a second segment 552 and an intermediatesegment 554. The first segment 550 is located a first predetermineddistance away from a reference plane 558 that is perpendicular to thelongitudinal axis of the rotary selector cam 520 and the second segment552 is located a second distance away from the reference plane 558. Theintermediate segment 554 couples the first and second segments 550 and552 to one another. The configuration of first cam slot 540 b isidentical to that of first cam slot 540 a, except that it is rotatedrelative to the rotary selector cam 520 such that each of the first,second and intermediate segments 550, 552 and 554 in the first cam slot540 b are located 180° apart from the first, second and intermediatesegments 550, 552 and 554 in the first cam slot 540 a.

Each of the second cam slots 544 a and 544 b is sized to receive one ofthe tabs 526 of a corresponding one of the wire clips 522. In theparticular embodiment illustrated, second cam slot 544 a includes afirst segment 560, a second segment 562, a third segment 564 and a pairof intermediate segments 566 and 568. The first and third segments 560and 564 are located a third predetermined distance away from thereference plane and the second segment 562 is located a fourth distanceaway from the reference plane 558. The intermediate segment 566 acouples the first and second segments 560 and 562 to one another and theintermediate segment 568 couples the second and third segments 562 and566 together. The configuration of second cam slot 544 b is identical tothat of second cam slot 544 a, except that it is rotated relative to therotary selector cam 520 such that each of the first, second, third andintermediate segments 560, 562, 564 and 566 and 568 in the second camslot 544 b are located 180° apart from the first, second, third andintermediate segments 560, 562, 564 and 566 and 568 in the second camslot 544 a.

With the tabs 526 of the wire clips 522 engaged to the first cam slots540 a and 540 b and the second cam slots 544 a and 544 b, the rotaryselector cam 520 may be rotated on the transmission sleeve 200 betweenthe first, second and third positions 500, 502 and 504 to selectivelyengage and disengage the second and third ring gears 360 and 400 fromthe first and third reduction carriers 314 and 404, respectively. Duringthe rotation of the rotary selector cam 520, the first cam slots 540 aand 540 b and the second cam slots 544 a and 544 b confine the wire tabs526 of their associated wire clip 522 and cause the wire tabs 526 totravel along the longitudinal axis of the transmission sleeve 200 in anassociated one of the first and second clip slots 284 and 286.Accordingly, the rotary selector cam 520 is operative for converting arotational input to an axial output that causes the wire clips 522 tomove axially in a predetermined manner. A lubricant (not specificallyshown) is applied to the lubricant grooves 252 formed into body portion246 of the transmission sleeve 200 is employed to lubricate theinterface between the transmission sleeve 200 and the rotary selectorcam 520.

Positioning the rotary selector cam 520 in the first rotational position500 causes the tabs 526 of the wire clip 522 that is engaged to thesecond ring gear 360 to be positioned in the first segment 550 of thefirst cam slots 540 a and 540 b and the tabs 526 of the wire clip 522that is engaged to the third ring gear 400 to be positioned in the firstsegment 560 of the second cam slots 544 a and 544 b. Accordingly,positioning of the rotary selector cam 520 in the first rotationalposition causes the second and third ring gears 360 and 400 to bepositioned in meshing engagement with the second and third planet gears362 and 402, respectively. Simultaneously with the meshing engagement ofthe second and third ring gears 360 and 400 with the second and thirdplanet gears 362 and 402, the sleeve engagement teeth 370 and 418 of thesecond and third ring gears 360 and 400, respectively, are positioned inmeshing engagement with the first and second sets of ring engagementteeth 254 and 256, respectively, to inhibit relative rotation betweenthe second and third ring gears 360 and 400 and the transmission sleeve200 to thereby providing the transmission assembly 16 with a firstoverall gear reduction or speed ratio 570 as shown in FIG. 23. Thoseskilled in the art will understand that the tip portion 272 of the teeth268 of the first and second sets of ring engagement teeth 254 and 256and the tip portions 372 and 420 of the sleeve engagement teeth 370 and418, respectively, are rounded and tapered so as to improve theircapability for meshing engagement in response to axial repositioningalong a longitudinal axis of the transmission assembly 16.

Positioning the rotary selector cam 520 in the second rotationalposition 502 causes the tabs 526 of the wire clip 522 that is engaged tothe second ring gear 360 to be positioned in the first segment 550 ofthe first cam slots 540 a and 540 b and the tabs 526 of the wire clip522 that is engaged to the third ring gear 400 to be positioned in thesecond segment 562 of the second cam slots 544 a and 544 b. Accordingly,positioning of the rotary selector cam 520 in second rotational positioncauses the second ring gear 360 to be in meshing engagement with thesecond planet gears 362 and the third ring gear 400 in meshingengagement with both the third planet gears 402 and the third reductioncarrier 404. Positioning of the rotary selector cam 520 in the secondrotational position 502 also positions the sleeve engagement teeth 370of the second ring gear 360 in meshing engagement with the first set ofring engagement teeth 254 while the sleeve engagement teeth 418 of thethird ring gear 400 are not meshingly engaged with the second set ofring engagement teeth 256. As such, relative rotation between the secondring gear 360 and the transmission sleeve 200 is inhibited, whilerelative rotation between the third ring gear 400 and the transmissionsleeve 200 is permitted to thereby provide the transmission assembly 16with a second overall gear reduction or speed ratio 572 as illustratedin FIG. 24.

Positioning the rotary selector cam 520 in the third rotational position504 causes the tabs 526 of the wire clip 522 that is engaged to thesecond ring gear 360 to be positioned in the second segment 552 of thefirst cam slots 540 a and 540 b and the tabs 526 of the wire clip 522that is engaged to the third ring gear 400 to be positioned in the thirdsegment 564 of the second cam slots 544 a and 544 b. Accordingly,positioning of the rotary selector cam 520 in the third rotationalposition causes the second ring gear 360 to be in meshing engagementwith both the second planet gears 362 and the first reduction carrier314 while the third ring gear 400 in meshing engagement with only thethird planet gears 402. Positioning the rotary selector cam 520 in thethird rotation position 504 also positions the sleeve engagement teeth370 on the second ring gear 360 out of meshing engagement with the firstset of ring engagement teeth 254 and the sleeve engagement teeth 418 onthe third ring gear 400 in meshing engagement with the second sets ofring engagement teeth 256 to inhibit relative rotation between thesecond ring gear 360 and the transmission sleeve 200 and permit relativerotation between the third ring gear 400 and the transmission sleeve 200to provide the transmission assembly 16 with a third overall gearreduction or speed ratio 574.

In the example shown in FIGS. 13, 27 b and 28, the spring member 523 isformed from a flat rectangular piece of spring steel and includes aflattened Z-shaped portion 580 and a raised portion 584. The flattenedZ-shaped portion 580 is configured to wrap around two reinforcement bars586 that extend into the spring aperture 546, thereby permitting theraised portion 584 to be maintained at a predetermined position and alsoto transmit a spring force between the rotary selector cam 520 and thespring member 523. With additional reference to FIG. 28, the raisedportion 584 of the spring member 523 is sized to engage internal notches590 formed in the housing 592 of the output spindle assembly 20. Lands594 that are circumferentially spaced from the rotary selector cam 520are formed between the notches 590. When the output spindle assembly 20is positioned over the transmission assembly 16 and the speed selectormechanism 60 is positioned in one of the first, second and thirdrotational positions 500, 502 and 504, the raised portion 584 of thespring member 523 engages an associated one of the notches 590. Theforce that is generated by the spring member 523 when the raised portion584 is moved downwardly toward the rotary selector cam 520 in responseto contact between the raised portion 584 and the land 594 acts toinhibit unintended rotation of the speed selector mechanism 60.Furthermore, placement of the raised portion 584 in a notch 590 providesthe user with a tactile indication of the positioning of the rotaryselector cam 520.

In the particular embodiment illustrated in FIGS. 13 and 27c, switchportion 510 is shown to include an arcuate band 600 having a raisedhollow and rectangular selector button 602 formed therein. The arcuateband 600 is formed from a plastic material and is configured to conformto the outer diameter of the rotary selector cam 520. The open end ofthe selector button 602 is configured to receive the switch tab 532,thereby permitting the switch portion 510 and the rotary selector cam520 to be coupled to one another in a fastenerless manner. The pluralityof spacing members 534 are raised portions formed into the rotaryselector cam 520 that are concentric to and extend radially outwardlyfrom the selector body 530. The spacing members 534 elevate the arcuateband 600 to prevent the arcuate band from contacting the wire tabs 526in the first cam slots 540 a and 540 b. The spacing members 534 may alsobe employed to selectively strengthen areas of the rotary selector cam520, such as in the areas adjacent the first cam slots 540 a and 540 b.

Those skilled in the art will understand that the rotary selector cam520 (i.e., the first cam slots 540 a and 540 b and the second cam slots544 a and 544 b) could be configured somewhat differently so as to causethe second ring gear 360 meshingly engages both the second planet gears362 and the first reduction carrier 314 while the third ring gear 400meshingly engages both the third planet gears 402 and the thirdreduction carrier 404 to thereby providing the transmission assembly 16with a fourth overall gear reduction or speed ratio.

Those skilled in the art will also understand that selector mechanismsof other configurations may be substituted for the selector mechanism 60illustrated herein. These selector mechanisms may include actuators thatare actuated via rotary or sliding motion and may include linkages, camsor other devices that are well known in the art to slide the second andthird ring gears 360 and 400 relative to the transmission sleeve 200.Those skilled in the art will also understand that as the second andthird ring gears 360 and 400 are independently movable between theactive and inactive modes (i.e., the placement of one of the second andthird ring gears 360 and 400 does not dictate the positioning of theother one of the second and third ring gears 360 and 400), the switchmechanism 60 could also be configured to position the second and thirdring gears 360 and 400 independently of one another.

Clutch Mechanism

In FIGS. 23, 26 and 28 through 30, the clutch mechanism 18 is shown toinclude a clutch member 700, an engagement assembly 702 and anadjustment mechanism 704. The clutch member 700 is shown to be anannular structure that is fixed to the outer diameter of the first ringgear 310 and which extends radially outwardly therefrom. The clutchmember 700 includes an arcuate clutch face 316 that is formed into thefront face 318 of the first ring gear 310. The outer diameter of theclutch member 700 is sized to rotate within the portion of the hollowcavity 212 that is defined by the base 216 of the transmission sleeve200. With specific brief reference to FIG. 29, the clutch face 316 ofthe example illustrated is shown to be defined by a plurality of peaks710 and valleys 712 that are arranged relative to one another to form aseries of ramps that are defined by an angle of about 18°. Those skilledin the art will understand, however, that other clutch faceconfigurations may also be employed, such as a sinusoidally shapedclutch face 316′ (FIG. 29a).

While the first ring gear 310 and the clutch member 700 have beenillustrated as a one piece (i.e., unitarily formed) construction, thoseskilled in the art will understand that they may be constructedotherwise. One such embodiment is illustrated in FIG. 29b wherein thefirst ring gear 310′ is shown to include an annular collar 1000 and aplurality of tab apertures 1002. The annular collar 1000 is illustratedto include a plurality of ramps 1004 that have dual sloping sides, butis otherwise flat. The first ring gear 310′ is otherwise identical tothe first ring gear 310. An annular damper 1008 abuts the annular collar1000 and includes a plurality of tab members 1010 that engage the tabapertures 1002 in the first ring gear 310′ to prevent the damper 1008from rotating relative to the first ring gear 310′. The damper 1008includes a body portion 1012 that is configured to match the contour ofthe annular collar 1000 and as such, includes a plurality of matingramped portions 1014 that are configured to engage each of the ramps1004. The damper 1008 is formed from a suitable impact dampeningmaterial, such as acetyl. The clutch member 700′, which is an annularmember that is formed from a wear resistant material, such as hardened8620 steel, is disposed over the damper 1008. Like the damper 1008, theclutch member 700′ includes a plurality of tab members 1020, which lockinto the tab apertures 1002 to prevent rotation relative to the firstring gear 310′, and a plurality of mating ramped portions 1022. Themating ramped portions 1022 of the clutch member 700′, however, matinglyengage the mating ramped portions 1014 of the damper 1008. While theconstruction in this manner is more expensive relative to the previouslydescribed embodiment, it is more tolerant of high impact forces that areassociated with the operation of the clutch mechanism 18.

In the particular embodiment illustrated, the engagement assembly 702includes a pin member 720, a follower spring 722 and a follower 724. Thepin member 720 includes a cylindrical body portion 730 having an outerdiameter that is sized to slip-fit within the second portion 278 of theactuator aperture 274 that is formed into the pin housing portion 248 ofthe transmission sleeve 200. The pin member 720 also includes a tipportion 732 and a head portion 734. The tip portion 732 is configured toengage the adjustment mechanism 704 and in the example shown, is formedinto the end of the body portion 730 of the pin member 720 and definedby a spherical radius. The head portion 734 is coupled to the end of thebody portion 730 opposite the tip portion 732 and is shaped in the formof a flat cylinder or barrel that is sized to slip fit within the firstportion 276 of the actuator aperture 274. Accordingly, the head portion734 prevents the pin member 720 from being urged forwardly out of theactuator aperture 274.

The follower spring 722 is a compression spring whose outside diameteris sized to slip fit within the first portion 276 of the actuatoraperture 274. The forward end of the follower spring 722 contacts thehead portion 734 of the pin member 720, while the opposite end of thefollower spring 722 contacts the follower 724. The end portion 740 ofthe follower 724 is cylindrical in shape and sized to slip fit withinthe inside diameter of the follower spring 722. In this regard, the endportion 740 of the follower acts as a spring follower to prevent thefollower spring 722 from bending over when it is compressed. Thefollower 724 also includes a follower portion 744 having a cylindricallyshaped body portion 746, a tip portion 748 and a flange portion 750. Thebody portion 746 is sized to slip fit within the first portion 276 ofthe actuator aperture 274. The tip portion 748 is configured to engagethe clutch face 316 and in the example shown, is formed into the end ofthe body portion 746 of the follower 724 and defined by a sphericalradius. The flange portion 750 is formed at the intersection between thebody portion 746 and the end portion 740. The flange portion 750 isgenerally flat and configured to receive a biasing force that is exertedby the follower spring 722.

The adjustment mechanism 704 is also shown to include an adjustmentstructure 760 and a setting collar 762. The adjustment structure 760 isshaped in the form of a generally hollow cylinder that is sized to fit ahousing portion 766 of the output spindle assembly 20. The adjustmentstructure 760 includes an annular face 768 into which an adjustmentprofile 770 is formed. The adjustment profile 770 includes a firstadjustment segment 772, a last adjustment segment 774, a plurality ofintermediate adjustment segments 776 and a ramp section 778 between thefirst and last adjustment segments 772 and 774. In the embodimentillustrated, a second ramp section 779 is included between the lastintermediate adjustment segment 776 z and the last adjustment segment774. Also in the particular embodiment illustrated, the portion of theadjustment profile 770 from the first adjustment segment 772 through thelast one of the intermediate adjustment segments 776 z is formed as aramp having a constant slope. Accordingly, a follower 780 that iscoupled to the housing portion 766 of the output spindle assembly 20 isbiased radially outwardly toward the inside diameter of the adjustmentstructure 760 where it acts against the plurality of detents 782 thatare formed into the adjustment mechanism 704 (e.g., in the settingcollar 762). The follower 724 and plurality of detents 782 cooperate toprovide the user of tool 10 with a tactile indication of the position ofthe adjustment profile 770 as well as inhibit the free rotation of theadjustment structure 760 so as to maintain the position of theadjustment profile 770 at a desired one of the adjustment segments 772,774 and 776.

The setting collar 762 is coupled to the exterior of the adjustmentstructure 760 and includes a plurality of raised gripping surfaces 790that permit the user of the tool 10 to comfortably rotate both thesetting collar 762 and the adjustment structure 760 to set theadjustment profile 770 at a desired one of the adjustment segments 772,774 and 776. A setting indicator 792 is employed to indicate theposition of the adjustment profile 770 relative to the housing portion766 of the output spindle assembly 20. In the example provided, thesetting indicator 792 includes an arrow 794 formed into the housingportion 766 of the output spindle assembly 20 and a scale 796 that ismarked into the circumference of the setting collar 762.

During the operation of the tool 10, an initial drive torque istransmitted by the motor pinion 46 from the motor assembly 14 to thefirst set of planet gears 312 causing the first set of planet gears 312to rotate. In response to the rotation of the first set of planet gears312, a first intermediate torque is applied against the first ring gear310. Resisting this torque is a clutch torque that is applied by theclutch mechanism 18. The clutch torque inhibits the free rotation of thefirst ring gear 310, causing the first intermediate torque to be appliedto the first reduction carrier 314 and the remainder of the reductiongearset assembly 202 so as to multiply the first intermediate torque ina predetermined manner according to the setting of the switch mechanism60. In this regard, the clutch mechanism 18 biases the first reductiongearset 302 in the active mode.

The magnitude of the clutch torque is dictated by the adjustmentmechanism 704, and more specifically, the relative height of theadjustment segment 772, 774 or 776 that is in contact with the tipportion 732 of the pin member 720. Positioning of the adjustmentmechanism 704 at a predetermined one of the adjustment segments 772, 774or 776 pushes the pin member 720 rearwardly in the actuator aperture274, thereby compressing the follower spring 722 and producing the aclutch force. The clutch force is transmitted to the flange portion 750of the follower 724, causing the tip portion 748 of the follower 724 toengage the clutch face 316 and generating the clutch torque. Positioningof the tip portion 748 of the follower 724 in one of the valleys 712 inthe clutch face 316 operates to inhibit rotation of the first ring gear310 relative to the transmission sleeve 200 when the magnitude of theclutch torque exceeds the first intermediate torque. When the firstintermediate torque exceeds the clutch torque, however, the first ringgear 310 is permitted to rotate relative to the transmission sleeve 200.Depending upon the configuration of the clutch face 316, rotation of thefirst ring gear 310 may cause the clutch force to increase a sufficientamount to resist further rotation. In such situations, the first ringgear 310 will rotate in an opposite direction when the magnitude of thefirst intermediate torque diminishes, permitting the tip portion 748 ofthe follower 724 to align in one of the valleys 712 in the clutch face316. If rotation of the first ring gear 310 does not cause the clutchforce to increase sufficiently so as to fully resist rotation of thefirst ring gear 310, the first reduction gearset 302 will be placed inthe inactive mode wherein the first ring gear 310 will rotate so as toinhibit the transmission of the first intermediate torque to the firstreduction carrier 314. In such situations, no torque will be transmittedthrough the portions of the transmission assembly 16 that are locatedforwardly of the first set of planet gears 312 (e.g., the firstreduction carrier 314, the second sun gear 358, the second set of planetgears 362).

Configuration of the clutch mechanism 18 in this manner is highlyadvantageous in that the clutch torque is sized to resist the firstintermediate torque, as opposed to the output torque of the tool 10 thatis generated by the multi-reduction transmission assembly 16 andtransmitted through the chuck 22. In this regard, the clutch mechanism18 may be sized in a relatively small manner, thereby improving theability with which it can be incorporated or packaged into the tool 10.Furthermore, as the speed or gear ratios are changed after or downstream of the first ring gear 310, the clutch mechanism 18 is operableover a relatively large span of output torques. In comparison withconventional clutch mechanisms that operate to limit the output torqueof a transmission, these devices are typically operable over arelatively narrow torque band, necessitating a change in their clutchspring if a considerable shift in the magnitude of the output torque isdesired. In contrast, the clutch mechanism 18 of the present inventioncan accommodate a considerable shift in the magnitude of the outputtorque of the tool 10 by simply operating the transmission assembly 16in a different (i.e., lower or higher) gear ratio.

In the operation of rotary power tools such as tool 10, it is frequentlydesirable to change between two clutch settings, as when the tool 10 isused to both drill a hole and thereafter install a screw in that hole.Accordingly, the adjustment mechanism 704 may be rotated relative to theoutput spindle assembly 20 to position the adjustment mechanism 704 at adesired one of the adjustment segments 772, 774 and 776 to perform thefirst operation and thereafter rotated to a second one of the adjustmentsegments 772, 774 and 776 to perform the second operation. In contrastto the known clutch arrangements, the adjustment mechanism 704 of thepresent invention is configured such that the adjustment structure 760and the setting collar 762 are rotatable through an angle of 360°.Assuming the adjustment structure 760 to be positioned at anintermediate adjustment segment 776 x, rotation of the adjustmentmechanism 704 through an angle of 360° would rotate the adjustmentstructure 760 past the other intermediate adjustment segments 776, aswell as the first and last adjustment segments 772 and 774 and the rampsection 778 such that the adjustment structure 760 would again bepositioned at the intermediate adjustment segment 776 x. The feature isespecially convenient when it is necessary to change the clutch settingbetween a relatively high clutch setting and a relatively low clutchsetting. In this regard, the ramp section 778 permits the setting collar762 (and adjustment structure 760) to be rotated from highest clutchsetting, corresponding to the last adjustment segment, to the lowestclutch setting, corresponding to the first clutch setting, withoutpositioning the clutch mechanism 18 in one of the intermediate clutchsettings. Accordingly, the user of the tool 10 is able to vary theclutch setting from its maximum setting to its minimum setting (and viceversa) by rotating the setting collar 762 a relatively small amount.

While the adjustment profile 770 has been described thus far as having aconstant slope, those skilled in the art will appreciate that theinvention, in its broader aspects, may be constructed somewhatdifferently. For example, the adjustment profile 770′ may be formed suchthat each of the first, last and intermediate adjustment segments 772′,774′ and 776′ is detented as illustrated in FIG. 31. In thisarrangement, the detents 782 in the adjustment structure 760 and thefollower 780 in the housing portion 766 of the output spindle assembly20 are unnecessary as the adjustment segments 772′, 774′ and 776′ willcooperate with the engagement 702 to provide the user of the tool 10with a tactile indication of the position of the adjustment profile770′, as well as inhibit the free rotation of the adjustment structure760.

Another example is illustrated in FIG. 32 wherein the adjustment profile770″ is generally similar to the adjustment profile 770 except that theramp section 779 has been omitted so that the last intermediateadjustment segment 776 z is immediately adjacent the last adjustmentsegment 774.

While the invention has been described in the specification andillustrated in the drawings with reference to a preferred embodiment, itwill be understood by those skilled in the art that various changes maybe made and equivalents may be substituted for elements thereof withoutdeparting from the scope of the invention as defined in the claims. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment illustrated by the drawingsand described in the specification as the best mode presentlycontemplated for carrying out this invention, but that the inventionwill include any embodiments falling within the description of theappended claims.

What is claimed is:
 1. A drive train for a power tool comprising: ahousing; a transmission including a first reduction gear set, a secondreduction gear set and a third reduction gear set, at least two of thefirst, second and third reduction gear sets being operable in aninactive mode and an active mode for performing a speed reduction andtorque multiplication operation; and a speed selector mechanism having aswitch portion and an actuator portion, the switch portion being coupledto the housing for movement between a first position, a second positionand a third position, the actuator portion operatively coupled to thetransmission and moving at least two of the first, second and thirdreduction gear sets between the active and inactive modes in response tomovement of the switch portion between the first, second and thirdpositions.
 2. The drive train of claim 1, wherein the transmission isoperable at a first rotational speed when the switch portion is in thefirst position, a second speed when the switch portion is in the secondposition and a third speed when the switch portion is in the thirdposition.
 3. The drive train of claim 2, wherein the speed selectormechanism moves two of the first, second and third reduction gear setsbetween the active and inactive modes and wherein the drive trainfurther includes a clutch that maintains the other one of the first,second and third reduction gear sets in the active mode unless a torqueexerted on the other one of the first, second and third reduction gearsets exceeds a predetermined clutch torque.
 4. The drive train of claim3, wherein the second and third reduction gear sets are the two of saidfirst, second and third reduction gear sets, wherein the second andthird reduction gear sets are active when the switch portion is in thefirst position, wherein the one of said second and third reduction gearsets is active and the other one of said second and third reduction gearsets is inactive when said switch portion is in the second position, andwherein both of said second and third reduction gear sets are inactivewhen the switch portion is in the third position.
 5. The drive train ofclaim 1, wherein at least one of the first, second and third reductiongear sets includes a ring gear, the ring gear being movable between afirst position fixed relative to the housing and a second positionrotatable relative to the housing, the ring gear being positioned at thefirst position when the at least one of the first, second and thirdreduction gear sets is in the active mode, the ring gear beingpositioned at the second position when the at least one of the first,second and third reduction gear sets is in the inactive mode.
 6. Thedrive train of claim 5, wherein each of the first, second and thirdreduction gear sets includes an associated ring gear.
 7. The drive trainof claim 1, wherein the switch portion is coupled to the housing forrotation between the first, second and third positions about a firstaxis.
 8. The drive train of claim 7, wherein the first axis is alongitudinal axis of the transmission.
 9. A transmission assembly fortransmitting torque to an output shaft in a power tool, the transmissionassembly comprising: a housing having a wall member that defines atransmission bore; a first transmission portion having a first inputmember, a first output member and a first reduction element, the firstinput member configured to receive a first intermediate output torque,the first output member configured to output a second intermediateoutput torque, the first reduction element operable in a first conditionwherein the first transmission portion multiplies the first intermediateoutput torque by a predetermined first amount, the first reductionelement further operable in a second condition wherein the firsttransmission portion multiplies the first intermediate output torque bya predetermined second amount; and a second transmission portion havinga second input member, a second output member and a second reductionelement, the second input member configured to receive the secondintermediate output torque, the second output member configured tooutput an output torque to the output shaft, the second reductionelement operable in a first condition wherein the second transmissionportion multiplies the second intermediate output torque by apredetermined third amount, the second reduction element furtheroperable in a second condition wherein the second transmission portionmultiplies the second intermediate output torque by a predeterminedfourth amount; wherein the first and second reduction elements areselectively positionable to provide the transmission assembly with atleast three speed ratios.
 10. The transmission assembly of claim 9,wherein at least one of the first and second transmission portions is aplanetary gear assembly.
 11. The transmission assembly of claim 9,wherein at least one of the first and second reduction elements is aring gear.
 12. The transmission assembly of claim 11, wherein the ringgear is slidable in an axial direction that is parallel to alongitudinal axis of the transmission bore.
 13. The transmissionassembly of claim 12, wherein the ring gear is slidable between a firstposition, wherein the ring gear is fixed relative to the housing, and asecond position, wherein the ring gear is rotatable within the housing.14. The transmission assembly of claim 9, wherein the first and secondreduction elements are independently movable between their first andsecond conditions.
 15. The transmission assembly of claim 9, wherein thefirst intermediate torque output is provided by another portion of thetransmission assembly.
 16. The transmission assembly of claim 15,further comprising a third transmission portion having a third inputmember, a third output member and a third reduction element, the thirdinput member configured to receive an input torque, the third outputmember configured to output the first intermediate output torque, thethird reduction element operable in a first condition wherein the thirdreduction element is fixed relative to the housing to permit the thirdtransmission portion to multiply the input torque by a fifthpredetermined amount.
 17. The transmission assembly of claim 16, whereinthe third reduction element is further operable in a second conditionwherein the third reduction element is movable relative to the housingto inhibit the third transmission portion from multiplying the inputtorque by the fifth predetermined amount.
 18. The transmission assemblyof claim 17, further comprising a clutch assembly having an annularflange and an engagement assembly, the annular flange coupled to one ofthe first, second and third reduction elements and having apredetermined clutch profile, the engagement assembly having a followermember, the follower member abutting the annular flange and cooperatingwith the clutch profile to inhibit relative rotation between the annularflange and the follower member when a torque is applied to the one thefirst, second and third reduction elements having a magnitude that isless than a predetermined maximum torque.
 19. A power tool comprising: ahousing having a wall member that defines a transmission bore; and atransmission having a first planetary gear set and a second planetarygear set: the first planetary gear set including a first ring gear, afirst sun gear and a first planet gear assembly, the first planet gearassembly having a first planet carrier and a plurality of first planetgears, the first planet carrier having an output sun gear and aplurality of pinions for rotatably supporting the plurality of firstplanet gears, the first sun gear configured to receive a firstintermediate output torque, the output sun gear configured to output asecond intermediate output torque, the plurality of first planet gearsmeshingly engaged with the first sun gear and the first ring gear, thefirst ring gear axially positionable in a first condition wherein thefirst ring gear is fixed relative to the housing to prevent relativerotation therebetween, the first ring gear also axially positionable ina second condition wherein the first ring gear is rotatable within thetransmission bore; and the second planetary gear set including a secondring gear and a second planet gear assembly, the second planet gearassembly having a second planet carrier and a plurality of second planetgears, the second planet carrier having an output member and a pluralityof pinions for rotatably supporting the plurality of second planetgears, the plurality of second planet gears meshingly engaged with thesecond ring gear and the output sun gear and configured to receive thesecond intermediate output torque, the output member configured tooutput an output torque, the second ring gear axially positionable in afirst condition wherein the second ring gear is fixed relative to thehousing to prevent relative rotation therebetween, the second ring gearalso axially positionable in a second condition wherein the second ringgear is rotatable within the transmission bore; wherein each of thefirst and second ring gears is selectively positionable in the first andsecond conditions to provide the power tool with at least threeoperating speeds.
 20. The power tool of claim 19, wherein the first andsecond ring gears are independently movable between their first andsecond conditions.
 21. The power tool of claim 19, wherein thetransmission further comprises a third planetary gear set having a thirdring gear, a third sun gear and a third planet gear assembly, the thirdplanet gear assembly having a third planet carrier and a plurality ofthird planet gears, the third planet carrier rotatably coupled to thefirst sun gear, the third planet carrier having a plurality of pinionsfor rotatably supporting the plurality of third planet gears, the thirdsun gear adapted to receive an input torque, the third planet carrieradapted to transmit the first intermediate output torque to the firstsun gear, the plurality of third planet gears meshingly engaged with thethird sun gear and the third ring gear, the third ring gear axiallypositionable in a first condition wherein the third ring gear is fixedrelative to the housing.
 22. The power tool of claim 21, wherein thethird planet gear reduction element is further operable in a secondcondition wherein the third ring gear is rotatable within the housing.23. The power tool of claim 22, further comprising a clutch assemblyhaving an annular flange and an engagement structure, the annular flangecoupled to one of the first, second and third ring gears and having apredetermined clutch profile, the engagement structure having a followermember, the follower member abutting the annular flange and cooperatingwith the clutch profile to inhibit relative rotation between the annularflange and the follower member when a torque is applied to the one thefirst, second and third ring gears having a magnitude that is less thana predetermined maximum torque.
 24. The power tool of claim 23, furthercomprising a switching assembly for coordinating the axial slidingmovement of the first and second ring gears.
 25. A power toolcomprising: a motor having an output shaft, the motor producing an inputtorque; a transmission assembly having a housing and a transmission, thehousing having a wall member that defines a transmission bore, thetransmission having a first planetary gear set, a second planetary gearset and a third planetary gearset, the first planetary gear set having afirst ring gear, a first sun gear and a first planet gear assembly, thefirst planet gear assembly having a first planet carrier and a pluralityof first planet gears, the first planet carrier rotatably coupled to thefirst sun gear, the first planet carrier having a plurality of pinionsfor rotatably supporting the plurality of first planet gears, the firstsun gear configured to receive the input torque, the first planetcarrier including a second sun gear and being configured to transmit thefirst intermediate output torque to the second planetary gear set, theplurality of first planet gears meshingly engaged with the second sungear and the first ring gear, the first ring gear axially positionablein a first condition wherein the first ring gear is fixed relative tothe housing, the second planetary gear set including a second ring gearand a second planet gear assembly, the second planet gear assemblyhaving a second planet carrier and a plurality of second planet gears,the second planet carrier having an output sun gear a plurality ofpinions for rotatably supporting the plurality of second planet gears,the second sun gear meshingly engaged with the plurality of second planegears and transmitting the first intermediate output torque thereto, theoutput sun gear adapted to output a second intermediate output torque,the plurality of second planet gears also being meshingly engaged withthe second ring gear, the second ring gear axially positionable in afirst condition wherein the second ring gear is fixed relative to thehousing to prevent relative rotation therebetween, the second ring gearalso axially positionable in a second condition wherein the second ringgear is rotatable within the transmission bore, the third planetary gearset including a third ring gear and a third planet gear assembly, thethird planet gear assembly having a third planet carrier and a pluralityof third planet gears, the third planet carrier having an output memberand a plurality of pinions for rotatably supporting the plurality ofthird planet gears, the plurality of third planet gears meshinglyengaged with the third ring gear and the output sun gear and configuredto receive the second intermediate output torque, the output memberadapted to output an output torque, the third ring gear axiallypositionable in a first condition wherein the third ring gear is fixedrelative to the housing to prevent relative rotation therebetween, thethird ring gear also being axially positionable in a second conditionwherein the third ring gear is rotatable within the transmission bore,wherein each of the second and third ring gears is selectivelypositionable in the first and second conditions to provide the powertool with at least three operating speeds.
 26. The power tool of claim25, wherein the first ring gear is further operable in a secondcondition wherein the first ring gear is rotatable relative to thehousing.
 27. The power tool of claim 25, wherein the transmissionassembly further comprises a clutch assembly having an annular flangeand an engagement assembly, the annular flange coupled to one of thefirst, second and third ring gears and having a predetermined clutchprofile, the engagement assembly having a follower member, the followermember abutting the annular flange and cooperating with the clutchprofile to inhibit relative rotation between the annular flange and thefollower member when a torque is applied to the one the first, secondand third ring gears having a magnitude that is less than apredetermined maximum torque.
 28. The power tool of claim 27, furthercomprising a switching assembly for coordinating the axial slidingmovement of the second and third ring gears.